The present invention relates to a method and apparatus for the early termination of frame data, and more specifically for deleting frame data from data memory when the frame data has not been transmitted from a transmitting network station or causing the deletion of the frame data from the memory of the receiving network station.
Network interfaces handle the transmission and reception of frame data between a transmitting network station and a receiving network station via a network communications system, such as a local area network. For transmission, frame data is sent from an upper layer down through a driver layer, a media access controller layer and then to a physical layer. In the transmitting network station, a central processor unit writes frame data and associated descriptors into system memory where a network interface reads the frame data and transmits the frame data onto the network. At the receiving network station a network interface stores the frame data into memory.
Typically, the central processor unit in the transmitting network station writes all of the information, i.e., frame data and associated descriptors, into system memory, and the network interface subsequently reads and writes all of that information into data memory. Once all of the information is written into data memory, the network interface starts to read and transmit the data frames. Reading and writing all of the information first into the system memory and subsequently into data memory requires a large amount of time. The larger the amount of information there is, the larger the amount of time required to transmit the information. In order to shorten this time, a media access controller in the network interface could read the stored information in the data memory before all of the information can be written in the data memory. However, because the network interface is unable to delete frame data that is in the process of being read or transmitted, the media access controller in the network interface cannot start to read the stored information before the central processing unit as finished writing the information into system memory.
There is a need for a media access controller in a network interface of a transmitting network station which has the ability to start to read frame data before all of the frame data is written into system memory.
There is also a need for a network interface in a transmitting network interface to have the ability to delete frame data that is read from data memory.
There is also a need for a network interface in a transmitting network interface to have the ability to cause the deletion of frame data being transmitted to another network interface.
These and other needs are attained by the present invention, where a network interface in a transmitting network station is able to delete frame data in data memory when the transmission of the frame data has not begun and is able to cause a receiving network interface to delete the frame data if the transmission of the frame data has begun.
According to one aspect of the present invention, a network interface comprising a data memory configured for storing at least one frame data, a media access controller (MAC) configured for transmitting a selected frame data in the data memory, a memory controller configured for determining the status of the selected frame data, and a descriptor management unit are used to delete frame data. The descriptor management unit is configured for reading and interpreting a descriptor associated with the selected frame data and contains a termination field containing information indicating if the selected frame data is to be deleted. The descriptor management unit is further configured to cause the MAC to append an inverted frame check sequence to the selected frame data when the selected frame data is to be deleted and transmission of data has already been initiated by the MAC or delete the selected frame data from the data memory when the transmission of the selected frame data has not been initiated and the selected frame data is to be deleted. The ability to delete the frame data allows the MAC in the network interface of the transmitting network station to initiate reading the frame data from the data memory before the central processing unit has written all of the frame data and associated descriptors into system memory.
Another aspect of the present invention provides a method for terminating a transmission of a selected frame in a network interface. The method comprises the steps of reading information in a termination field of a descriptor associated with a selected frame data, determining the status of the selected frame data and deleting the selected frame data when the termination field information in the descriptor for the associated selected frame data indicates the selected frame data is to be deleted and the status of the selected frame indicates that the selected frame data is scheduled for transmission. The method also includes the step of appending an inverted frame check sequence to the selected frame data when the termination field information indicates the selected frame data is to be deleted and the status of the selected frame indicates that the selected frame data is being transmitted. The ability to delete or cause the deletion of frame data by a network interface regardless of whether or not the transmitting network station has started the transmission of the frame data allows the network interface to respond to errors in a more efficient manner.
Another aspect of the present invention provides a network arrangement comprising a first station and a second station having network interfaces to delete selected frame data. The first station has a network interface comprising a first media access controller (MAC) configured for transmitting selected frame data, a descriptor management unit configured for reading and interpreting a descriptor associated with the selected frame data and containing a termination field containing information indicating if the selected frame data is to be deleted, and further configured to cause the first MAC to append an inverted frame check sequence to the selected frame data when the selected frame data is to be deleted and transmission of data has already been initiated by the first MAC, or delete the selected frame data from the data memory when the transmission of the selected frame data has not been initiated and the selected frame data is to be deleted. The second station has a network interface containing a second MAC configured for responding to receipt of the selected frame data with an appended inverted frame check sequence from the first station by deleting the received selected frame data. The ability to append the inverted frame check sequence allows the network interface to read the frame data while a central processing unit is writing frame data into system memory.
Additional advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.